Objective: To investigate factors predicting spontaneous clearance of residual renal fragments after flexible ureteroscopy.
Methods: Among 546 patients who underwent lithotripsy with flexible ureteroscopy, 81 had residual renal fragments, as determined by kidney-ureter-bladder films on postoperative day 1. The final outcome was determined at 3 months after the last flexible ureteroscopy session using non-contrast computed tomography. Patient characteristics and preoperative factors were analyzed using the unpaired t-test and χ(2)-test. Correlations between the possible predictive factors and the spontaneous clearance of residual renal fragments after flexible ureteroscopy were analyzed using a multivariate logistic regression model with backward selection.
Results: Non-contrast computed tomography at postoperative month 3 showed that 33 cases (40.7%) had spontaneous clearance of residual renal fragments, whereas 48 (59.3%) showed non-clearance. Significant differences were found between these cases in terms of stone number, stone location, presence of lower pole calculi and preoperative stent placement. Multivariate assessment showed that stone number (P = 0.004), presence of lower pole calculi (P = 0.021) and presence of hydronephrosis (P = 0.024) were independent predictors of the spontaneous clearance of residual renal fragments after flexible ureteroscopy.
Conclusions: Stone number, presence of lower pole calculi and presence of hydronephrosis are independent predictive factors of the spontaneous clearance of residual renal fragments after flexible ureteroscopy.
Keywords: computed tomography; helical; kidney stone; lithotripsy; multivariate analysis; ureteroscopy.
© 2015 The Japanese Urological Association.